Most photographic film now used is 35 mm format film. Cameras have been developed to allow film of this format to be easily loaded by placing the film cassette, in which the film is stored, into an opening in the back of the camera and then shutting the back of the camera. As a free end or tongue of the film extends externally to the film cassette, this is used to automatically advance the film in the camera for picture taking. Once all the pictures have been taken, the film is rewound into the film cassette for removal from the camera for processing. In order for this to work, the free end or tongue of the film must extend externally to the cassette so that it can be pulled on to the take-up spool in the camera as the film is first loaded.
Photographic film tends to be processed in a single strip once the film has been removed from its cassette. Strips of negative film are processed by transporting them, either as a single individual strip or as a continuous length comprising two or more strips of shorter lengths, through a series of processing solutions in various tanks in the processing apparatus.
In known processing apparatus, the film strip is pulled through tanks containing the processing solutions either by a leader which is attached to the leading edge of the film strip, or by moving a rack or spiral containing the film strip from tank to tank. Individual film strips may be pre-spliced into a long reel with a leader card at the front end, clipped to a rack, or fed into a spiral.
Where the film strip is attached to a leader, it is unloaded from the cassette and attached to the leader in a manual operation. The leader is then fed into the processing apparatus so that the film can be processed as it is transported through the apparatus.
Operations of splicing the film strips together or attaching the leader to the strip need to be carried out in darkroom conditions due to the sensitive nature of the film.
GB-A-1 469 000 discloses a film handling arrangement which allows the film to be unloaded from its cassette and loaded into the processing apparatus. The film handling arrangement includes a take-up reel to which the free end of the film is connected. The film is withdrawn from the cassette into the take-up reel and is cut from the spool to allow the film to be contained within the take-up reel, the cutting mechanism being actuated by tension applied to the film as it is withdrawn from the cassette.
The take-up reel described in GB-A-1 469 000 comprises a barrel for supporting the film and allowing it to be rotated in a reservoir of processing chemicals to develop the latent image stored on the film.
However, in some processing apparatus, there is a minimum length of film strip which can be processed. As a result, several film strips need to be spliced together prior to processing. This may be time-consuming as each strip will need to be measured to ensure that the minimum processing length is present in the spliced strip prior to processing.
It is therefore an object of the present invention to provide a loading device for a photographic processing apparatus in which the film strip is automatically unloaded from its cassette, its length checked, and then fed into the processor if the film strip exceeds the minimum length under the control of the process computer.